<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        table
        {
            border-collapse: collapse;
            margin: 0 auto;
        }
        td
        {
           border: 1px solid black;
           width: 20px;
           height: 20px;
           text-align: center;
        }
        td:hover
        {
            border: 1px red solid;
            cursor: pointer;
        }
    </style>
</head>
<body>
    <table>
        <tr>
            <td>1</td>
            <td>2</td>
            <td>3</td>
        </tr>
        <tr>
            <td>4</td>
            <td>5</td>
            <td>6</td>
        </tr>
        <tr>
            <td>7</td>
            <td>8</td>
            <td>9</td>
        </tr>
    </table>
</body>
</html>